rs4994, also known as Trp64Arg or as the Arg64 variant, is a SNP in the ADRB3 gene. The rs4994(C) allele encodes the variant arginine.

In a study of 600+ women initially referred for coronary angiography and then followed for 6 years, during which time 115 experienced a heart problem, rs4994(C) individuals were calculated to be at higher risk (adjusted hazard ratio 2.10, CI: 1.05-4.24). This risk was due to subtle increases in risk for all of the individual endpoints, and was only seen in women without obstructive coronary artery disease.[PMID 18331634]